Perylene functionalized porphyrin dyes for dye-sensitized solar cells

ABSTRACT

The invention relates to dyes for dye-sensitized solar cells, and in particular, to perylene functionalized porphyrin dyes for dye-sensitized solar cells. The invention further relates to a dye molecule comprising perylene functionalized porphyrin moiety.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Singapore PatentApplication No. 201305268-3, filed Jul. 8, 2013, the contents of whichbeing hereby incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The invention relates to dyes for dye-sensitized solar cells, and inparticular, to perylene functionalized porphyrin dyes for dye-sensitizedsolar cells. The invention further relates to a dye molecule comprisingperylene functionalized porphyrin moiety.

BACKGROUND

Despite tremendous achievement in this area, dye-sensitized solar cells(DSSCs) suffer from some drawbacks which have prevented them fromfurther commercialization. The major problems are low efficiency andstability. The highest efficiency reported until recently for DSSCs is12.3%, which is around half as good as the best-known polycrystallineSi-cell (20.3%) and comparable to an amorphous Si-cell (9.5%). Theefficiency of DSSC is mainly limited by the light absorption of the dyesand the interface charge separations between dyes and TiO₂semiconductors. Hence, the key challenge to achieve high efficiencyDSSCs is the development of suitable organic dyes that has extendedlight absorption spectrum in the near infrared range and couldeffectively generate electricity from light.

SUMMARY

Presently disclosed is a series of perylene functionalized porphyrindyes for use in dye-sensitized solar cells (DSSCs). These dyes showedintense (molar extinction coefficient >5×10⁴ M⁻¹cm⁻¹) and broadabsorption in the visible and NIR range (350-900 nm). More than 11%power conversion efficiency has been achieved with the presentlydisclosed dyes and this is very close to the world record of 12.3%(Yella et al. Science 2011, 334, 629). Both the perylene moiety andporphyrin core have been found to be very important for their goodperformance in DSSCs.

Thus, in one aspect of the invention, there is provided a dye-sensitizedsolar cell comprising a dye molecule of Formula (I):

In Formula (I), M is zinc or cobalt. Alternatively, M may be, but notlimited to, nickel, iron, and copper. Each of L₁ and L₂ is a linker andmay be independently selected from the group consisting of a direct bondand an ethynylene group. Each of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ may beindependently selected from the group consisting of hydrogen, halogen,C₁₋₃₀ alkyl, and C₆-C₂₀ aryl. Each of R₉ and R₁₀ may be independently asubstituted or unsubstituted phenyl, or a substituted or unsubstitutedbenzyl. AG is an anchor group for attachment to a substrate.

In Formula (I), Pery is a perylene-based moiety of Formula (II):

In Formula (II), each of R₁₁ and R₁₂ may be independently a substitutedor unsubstituted phenyl, or a substituted or unsubstituted benzyl.

In another aspect of the invention, a dye molecule of Formula (I) isdisclosed. The dye molecule may be employed as light harvesting dyes andemployed in photocatalysis.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilydrawn to scale, emphasis instead generally being placed uponillustrating the principles of various embodiments. In the followingdescription, various embodiments of the invention are described withreference to the following drawings.

FIG. 1 shows a synthesis scheme for preparing present dye P1 and P2.

FIG. 2 shows a synthesis scheme for preparing present dye P3 and P4.

FIG. 3 shows device performance for various dyes P1, P2, and P3.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practised. These embodiments are described insufficient detail to enable those skilled in the art to practise theinvention. Other embodiments may be utilized and structural and chemicalchanges may be made without departing from the scope of the invention.The various embodiments are not necessarily mutually exclusive, as someembodiments can be combined with one or more other embodiments to formnew embodiments.

The key to achieve highly efficient dye-sensitized solar cells (DSSCs)is the design and synthesis of stable organic dyes with appropriatepush-pull structure. Moreover, the molecule needs to have broad andintense absorption, and also with appropriate energy levels tocomplement the electrodes and electrolyte for desired devicefabrication.

In one aspect of the invention, there is described a dye-sensitizedsolar cell comprising a dye molecule. The dye molecule comprises aporphyrin moiety, a perylene moiety, and an anchor group for attachmentto a substrate, which are coupled together via linkers. In particular,the perylene moiety is coupled to a first site of the porphyrin moietyvia a first linker and the anchor group is coupled to a second site ofthe porphyrin moiety via a second linker.

Herein disclosed organic dye molecules meet the above requirements dueto the following considerations:

Electron-donating groups result in a more red-shifted NIR absorption dueto the enhanced intramolecular charge transfer and is also beneficial toa fast electron injection. In present case, the perylene moiety isconsidered to be a particularly useful building block in organicelectronics due to their high photostability and strong absorptionability.

The term “porphyrin” refers to a cyclic structure typically composed offour pyrrole rings together with four nitrogen atoms and two replaceablehydrogens for which various metal atoms can readily be substituted.

The anchor group (such as, but not limited to aromatic carboxylic acidgroup) serves as a tight binding point for attaching the dye molecule tothe semiconductor layer in DSSCs (such as TiO₂ layer) and helps tostabilize the low band gap if-system of dyes.

Introduction of an ethynylene group, for example, as a linker into themeso-position of the porphyrin moiety would decrease HOMO-LUMO gap andimprove the charge separation in DSSCs.

Certain bulky substituents on the porphyrin moiety or perylene moiety,such as but not limited to 3,5-di-tert-butylphenyl,2,4,6-trimethylphenyl as well as ortho-alkoxy substituted phenyl groups,were chosen to surmount the solubility problem and reduce dyeaggregation in DSSCs.

Accordingly, the dye molecule has the general Formula (I) as shownbelow:

In Formula (I), M is a metal. In other words, the porphyrin moiety iscommonly termed a metalloporphyrin. In preferred embodiments, M is zincor cobalt. Alternatively, M may be, but not limited to, nickel, iron,and copper.

In Formula (I), AG is an anchor group for attachment to a substrate. Thesubstrate may be a solid material (which may be flexible or rigid)suitable for the attachment of one or more dye molecules. Substrates canbe formed of materials including, but not limited to glass, organicpolymers, plastic, silicon, minerals (e.g. quartz), semiconductingmaterials, ceramics, metals, etc. The substrate majr be in any suitableshape, including spherical, flat, planar, curved, rod-shaped, etc. Invarious embodiments, the substrate comprises a semiconducting materialparticle (including nanoparticle and microparticle), such as titaniumdioxide (TiO₂) attached to the AG. The attachment may be a chemical orphysical bond. For example, the attachment may be a covalent bond.

In preferred embodiments, AG may comprise a phenolic derivative ofbenzoic acid. For example, AG may be:

In various embodiments, in Formula (I), each of R₁, R₂, R₃, R₄, R₅, R₆,R₇, R₈ may be independently selected from the group consisting ofhydrogen, halogen, C₁₋₃₀ alkyl, and C₆-C₂₀ aryl.

In Formula (I), each of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ may be hydrogen.

In Formula (I), each of L₁ and L₂ is a linker wherein L₁ couples (orlinks) the Pery moiety to the porphyrin moiety and L₂ couples (or links)the porphyrin moiety to the AG.

In various embodiments, each of L₁ and L₂ may be a direct bond.

In other embodiments, each of L₁ and L₂ may be an ethynylene group (i.e.—C≡C—).

In further embodiments, L₁ may be a direct bond and L₂ may be anethynylene group.

In yet further embodiments, L₁ may be an ethynylene group and L₂ may bea direct bond.

In various embodiments, each of R₉ and R₁₀ may be a phenyl (i.e. —C₆H₅).The phenyl may be substituted or unsubstituted. For example, R₉ may be amono-, di-, tri-, tetra-, or penta-substituted phenyl. In anotherexample, R₁₀ may be a mono-, di-, tri-, tetra-, or penta-substitutedphenyl. In further examples, R₉, R₁₀ or both R₉ and R₁₀ may beunsubstituted phenyl.

In alternative embodiments, each of R₉ and R₁₀ may be a benzyl (i.e.—CH₂C₆H₅). The benzyl may be substituted or unsubstituted. For example,R₉ may be a mono-, di-, tri-, tetra-, or penta-substituted benzyl. Inanother example, R₁₀ may be a mono-, di-, tri-, tetra-, orpenta-substituted benzyl. In further examples, R₉, R₁₀ or both R₉ andR₁₀ may be unsubstituted benzyl.

In further embodiments, R₉ may be a phenyl and R₁₀ may be a benzyl. Thephenyl or benzyl may be unsubstituted or substituted as defined herein.

In yet further embodiments, R₉ may be a benzyl and R₁₀ may be a phenyl.The phenyl or benzyl may be unsubstituted or substituted as definedherein.

In various embodiments, R₉, or R₁₀, or both R₉ and R₁₀ are independentlyC₁₋₁₀ alkyl-substituted phenyl.

The term “alkyl”, alone or in combination, refers to a fully saturatedaliphatic hydrocarbon. In certain embodiments, alkyls are optionallysubstituted. In certain embodiments, an alkyl comprises 1 to 30 carbonatoms, for example 1 to 10 carbon atoms, wherein (whenever it appearsherein in any of the definitions given below) a numerical range, such as“1 to 30” or “C₁₋₃₀”, refers to each integer in the given range, e.g.“C₁₋₃₀ alkyl” means that an alkyl group comprising only 1 carbon atom, 2carbon atoms, 3 carbon atoms, etc., up to and including 30 carbon atoms.Examples of alkyl groups include, but are not limited to, methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl,hexyl, heptyl, octyl and the like.

The term “aryl” refers to an aromatic ring wherein each of the atomsforming the ring is a carbon atom. Aryl rings may be formed by five,six, seven, eight, nine, or more than nine carbon atoms. Aryl groups maybe optionally substituted. In various embodiments, any one (or more) ofR₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ may be a substituted or unsubstitutedC₆-C₂₀ aryl.

A “halo” or “halogen” group refers to fluorine, chlorine, bromine oriodine.

In preferred embodiments, R₉, or R₁₀, or both R₉ and R₁₀ areindependently methylphenyl (i.e. mono-substituted). The methyl may beortho-, meta-, or para-substituted on the phenyl.

In certain preferred embodiments, R₉, or R₁₀, or both R₉ and R₁₀ areindependently trimethylphenyl (i.e. tri-substituted). For example, R₉,or R₁₀, or both R₉ and R₁₀ may be 2,4,6-trimethyl phenyl .

In other embodiments, R₉, or R₁₀, or both R₉ and R₁₀ are independentlyC₁₋₁₅ alkoxy-substituted phenyl.

The term “alkoxy”, alone or in combination, refers to an aliphatichydrocarbon having an alkyl-O— moiety. In certain embodiments, alkoxygroups are optionally substituted. C₁₋₁₅ alkoxy therefore refers to analiphatic hydrocarbon having an alkyl-O— moiety, wherein the alkylcomprises 1 to 15 carbon atoms, for example 1 carbon atom, 2 carbonatoms, 3 carbon atoms, etc., up to and including 15 carbon atoms.Examples of alkoxy groups include, but are not limited to, methoxy,ethoxy, propoxy, butoxy and the like.

In preferred embodiments, R₉, or R₁₀, or both R₉ and R₁₀ areindependently octyloxyphenyl (i.e. mono-substituted). The octyloxy maybe ortho-, meta-, or para-substituted on the phenyl.

In certain preferred embodiments, R₉, or R₁₀, or both R₉ and R₁₀ areindependently di-octyloxyphenyl (i.e. di-substituted). For example, R₉,or R₁₀, or both R₉ and R₁₀ may be 2,6-di-octyloxyphenyl.

In yet further preferred embodiments, R₉, or R₁₀, or both R₉ and R₁₀ areindependently dodecyloxyphenyl (i.e. mono-substituted). The dodecyloxymay be ortho-, meta-, or para-substituted on the phenyl.

In certain preferred embodiments, R₉, or R₁₀, or both R₉ and R₁₀ areindependently di-dodecyloxyphenyl (i.e. di-substituted). For example,R₉, or R₁₀, or both R₉ and R₁₀ may be 2,6-di-dodecyloxyphenyl.

In Formula (I), Pery is a perylene-based moiety of Formula (II):

In Formula (II), each of R₁₁ and R₁₂ may be independently a substitutedor unsubstituted phenyl, or a substituted or unsubstituted benzyl.

In various embodiments, R₁₁ may be a benzyl and R₁₂ may be a phenyl.

In various embodiments, R₁₂ may be a mono-, di-, tri-, tetra, orpenta-substituted phenyl.

In preferred embodiments, R₁₂ is a C₁₋₁₀ alkyl-substituted phenyl.

In certain embodiments, R₁₂ is tert-butylphenyl.

In one preferred embodiment, R₁₂ is para-tert-butylphenyl.

In various embodiments, R₁₁ may be a mono-, di-, tri-, tetra, orpenta-substituted benzyl.

In preferred embodiments, R₁₁ is a C₁₋₁₀ alkyl-substituted benzyl.

In yet certain embodiments, R₁₁ is a di-C₁₋₁₀ alkyl-substituted benzyl.

In one embodiment, R₁₁ is 3,5-di-tert-buytibenzyl.

In other embodiments, R₁₁ may be a phenyl and R₁₂ may be a benzyl.

In yet further embodiments, both R₁₁ and R₁₂ may be phenyl or both R₁₁and R₁₂ may be benzyl.

In various preferred embodiments, the dye molecule has any one of thefollowing chemical representations:

In order that the invention may be readily understood and put intopractical effect, particular embodiments will now be described by way ofthe following non-limiting examples.

EXAMPLES

A series of perylene functionalized porphyrin dyes has been synthesizedand employed in dye-sensitized solar cells (DSSCs). More than 11%efficiency has been achieved with the present synthetic dye molecules.The demonstrated DSSC performance is within top 5% as reported. The dyesshowed broad absorption with one set at 800 nm. The HOMO and LUOMOorbitals are well separated. The dyes are stable and avoiddye-aggregation on device.

FIG. 1 shows a synthesis scheme for preparing present dye P1 and P2.

Porphyrin 1 (295 mg, 0.4 mmol), perylene 2 (271.5 mg, 0.4 mmol),Pd(PPh₃)₄ (46 mg, 0.04 mmol), and Cs₂CO₃ (260 mg, 0.8 mmol) were driedunder vacuum and then purged with argon. To this were added degassedtoluene (10 mL) and DMF (5 mL), and the mixture was stirred at 96° C.for 36 h. After cooling, water was added and the product was extractedwith ethyl acetate (3×30 mL). The organic layer was washed withsaturated brine and dried over anhydrous Na₂SO₄. The solvent was removedunder vacuum, and the residue was purified by column chromatography(silica gel, DCM/hexane=1:3) to give a purple solid as the couplingproduct 3a (362 mg), which was subjected to the subsequent brominationreaction. To a CHCl₃ (100 mL) and pyridine (3 mL) solution of 3a wasadded a CHCl₃ solution (50 mL) of N-bromosuccinimide (NBS) (56 mg, 0.32mmol) dropwise in 10 min at 0° C. Acetone (100 mL) was added to thereaction mixture, and the resulting solution was concentrated andchromatographed on a short slica gel with CHCl₃ as an eluent to allowisolation of brominated compound 3 (386 mg, 75% yield for two steps).Characterization for 3a: ¹H NMR (CDCl₃, 400 MHz) δ 10.21 (s, 1H), 9.37(d, J=4.5 Hz, 2H), 8.93 (d, J=4.4 Hz, 2H), 8.77 (m, 3H), 8.69 (m, 3H),8.54 (s, 1H), 8.30 (d, J=8.4 Hz, 1H), 7.88 (dd, J=15.1, 6.9 Hz, 2H),7.73 (d, J=8.1 Hz, 2H), 7.63 (d, J=8.2 Hz, 2H), 7.46 (m, 1H), 7.30-7.21(m, 8H), 5.98 (s, 2H), 2.63 (s, 6H), 1.89 (s, 6H), 1.83 (s, 6H), 1.49(s, 9H), 1.12 (s, 18H). ¹³C NMR (100 MHz, CHCl₃) δ 151.37, 151.10,150.07, 149.99, 149.91, 149.69, 139.29, 139.08, 138.92, 138.02, 137.43,137.06, 136.59, 133.56, 132.61, 132.53, 132.37, 132.06, 131.31, 131.21,130.83, 130.39, 129.99, 128.20, 127.68, 127.61, 126.57, 125.35, 125.15,124.77, 124.41, 123.47, 121.94, 121.68, 121.23, 120.50, 120.28, 118.92,118.74, 117.98, 117.34, 114.71, 105.41, 50.41, 34.70, 31.53, 31.32,21.75, 21.62, 21.45. IR (thin film) ν 2961.35 (CH₃), 2918.66 (CH₂),2864.69 (CH₃), 1600.41 (C═C), 1475.05 (C═N), 1380.19 (C(CH₃)₃), 1362.47(C(CH₃)₃), 1298.29 (CH₂), 1058.53 (Ph), 997.35 (Ph), 832.74 (Ph, para),798.99 (Ph, meta), 757.99 (Ph, meta), 723.42 (Ph, meta) cm⁻¹. HRMS(APCI): m/z=1206.5387 (M⁺+1) calcd. for C₈₃H₇₆N₅Zn: 1206.5399(error=−1.0 ppm). Characterization for 3: ¹H NMR (400 MHz, THF) δ 9.65(d, J=4.5 Hz, 2H), 8.83 (d, J=7.4 Hz, 1H), 8.72 (d, J=4.5 Hz, 4H), 8.63(d, J=4.5 Hz, 2H), 8.51 (d, J=4.4 Hz, 2H), 8.22 (d, J=8.3 Hz, 1H), 8.05(s, 1H), 7.82 (t, J=7.9 Hz, 1H), 7.68 (dd, J=25.6, 8.1 Hz, 4H),7.49-7.24 (m, 8H), 7.13 (d, J=8.3 Hz, 1H), 6.09 (s, 2H), 2.59 (s, 6H),1.89 (s, 6H), 1.86 (s, 6H), 1.48 (s, 9H), 1.12 (s, 18H). ¹³C NMR (100MHz, THF) δ 152.21, 151.39, 150.60, 150.46, 150.16, 149.65, 139.78,139.71, 139.29, 138.44, 137.81, 137.70, 137.55, 134.04, 133.47, 133.04,132.99, 131.86, 131.63, 131.34, 131.16, 130.89, 130.77, 130.32, 128.53,127.99, 126.50, 125.52, 124.92, 124.78, 124.61, 124.27, 123.83, 122.50,121.66, 121.51, 120.81, 120.68, 119.53, 118.25, 117.63, 115.18, 103.39,50.28, 34.82, 31.33, 31.22, 30.15, 21.47, 21.03. IR (thin film) ν2960.66 (CH₃), 2922.78 (CH₂), 2852.19 (CH₃), 1652.15 (C═C), 1459.10(C═N), 1362.45 (C(CH₃)₃), 1298.46 (CH₂), 1204.87 (CH₂), 1113.98 (CH₂),1079.29 (Ph), 997.50 (Ph), 827.72 (Ph, para), 798.00 (Ph, meta), 758.22(Ph, meta) cm⁻¹. HRMS (APCI): m/z=1284.4492 (M⁺+1) calcd. forC₈₃H₇₅BrN₅Zn: 1284.4499 (error=−0.5 ppm).

A 50 mL round bottle flask was charged with 3 (64 mg, 0.05 mmol),4-ethynylbenzoic acid(29.2 mg, 0.2 mmol), Pd(RPh₃)₄ (6 mg, 0.005 mmol),Et₃N (4 mL) and THF (20 mL) under argon. The reaction mixture wasstirred at 50° C. for 24 hours. After removal of the solvents, the crudeproduct was purified by column chromatography (silica gel,DCM:MeOH=50:1) to give the purple solid product P1(48 mg, 70%yield).Characterization for P1: ¹H NMR (400 MHz, THF) δ 9.78 (d, J=4.5Hz, 2H), 8.90-8.68 (m, 5H), 8.62 (d, J=4.5 Hz, 2H), 8.48 (d, J=4.5 Hz,2H), 8.31-8.12 (m, 5H), 8.06 (s, 1H), 7.83 (t, J=7.9 Hz, 1H), 7.69 (dd,J=26.2, 8.1 Hz, 4H), 7.49-7.25 (m, 8H), 7.13 (d, J=8.3 Hz, 1H), 6.11 (s,2H), 2.60 (s, 6H), 1.92 (s, 6H), 1.90 (s, 6H), 1.49 (s, 9H), 1.14 (s,18H). ¹³C NMR (100 MHz, THF) δ 167.38, 153.21, 152.24, 152.15, 151.35,150.93, 150.62, 140.49, 140.01, 139.96, 139.19, 138.59, 138.44, 138.27,134.77, 133.72, 132.38, 132.23, 131.93, 131.64, 131.06, 130.02, 129.28,128.74, 127.26, 126.28, 125.67, 125.52, 124.57, 123.26, 122.42, 122.27,121.94, 121.44, 120.91, 119.00, 118.37, 115.94, 98.77, 97.39, 95.97,51.03, 35.58, 35.32, 32.08, 31.97, 22.21, 21.78. IR (thin film) ν3294.00 (OH), 2960.82 (CH₃), 2915.50 (CH₂), 2864.11 (CH₃), 2185.58(C≡C), 1690.98 (C═O), 1602.45 (C═C), 1475.08 (CH₂), 1436.96 (C═N),1362.10 (C(CH₃)₃), 1297.44 (CH₂), 1273.74 (Ph), 1205.21 (CH₂), 1172.82(Ph), 994.94 (Ph), 856.28 (Ph, para), 797.23 (Ph, meta), 756.56 (Ph,meta), 717.10 (Ph, meta), 694.58 (Ph, meta), 540.74 (Zn-N) cm⁻¹. HRMS(APCI): m/z=1350.5609 (M⁺+1) calcd. for C₉₂H₈₀N₅O₂Zn: 1350.5598(error=+0.8 ppm).

To a solution of 3 (128 mg, 0.1 mmol) in degassed anhydrousdichloroethane (40 mL) was added a FeBr₃ (59 mg, 0.2 mmol). The reactionmixture was carried out at room temperature for 24 h and then quenchedby addition of a saturated NaHCO₃ solution. The organic layer was washedwith saturated brine and dried over anhydrous Na₂SO₄. The solvent wasremoved under vacuum and the residue was purified by columnchromatography (silica gel, DCM:hexane=1:4) to give a brown solid as thering fused product (37 mg). To this brown solid in a 50 mL round bottleflask was added 4-ethynylbenzoic acid (17 mg, 0.12 mmol), Pd(PPh₃)₄ (4mg, 0.003 mmol), Et₃N (4 mL) and THF (20 mL) under argon. The reactionmixture was stirred at 50° C. for 24 hours. After removal of thesolvents, the crude product was purified by column chromatography(silica gel, DCM:MeOH=50:1) to give the dark brown solid product P2 (31mg, 23% yield in two steps). Characterization for P2: ¹H NMR (400 MHz,THF) δ 9.64-9.49 (m, 2H), 9.25 (d, J=14.0 Hz, 2H), 9.12 (br, 1H), 9.04(s, 1H), 8.77 (s, 1H), 8.57 (dd, J=11.7, 4.4 Hz, 2H), 8.47 (s, 1H), 8.30(d, J=5.8 Hz, 1H), 8.21 (d, J=7.9 Hz, 2H), 8.16-8.00 (m, 4H), 7.69 (br,5H), 7.56 (s, 2H), 7.49 (s, 1H), 7.39 (s, 2H), 7.36 (s, 2H), 6.33 (s,2H), 2.70 (s, 3H), 2.67 (s, 3H), 1.99 (s, 6H), 1.97 (s, 6H), 1.47 (s,9H), 1.23 (s, 18H). ¹³C NMR was not taken due to the compound lowsolubility. IR (thin film) ν 3640.43 (OH), 2955.43 (CH₃), 2913.45 (CH₂),2869.65 (CH₃), 2187.13 (C≡C), 1719.62 (C═O) 1443.92 (CH₂), 1430.93(C═N), 1360.38 (C(CH₃)₃), 1311.10 (CH₂), 1246.39 (Ph), 1231.02 (Ph),1213.08 (Ph), 1150.24 (Ph), 862.19 (Ph, para), 774.49 (Ph, meta), 768.67(Ph, meta) 577.77 (Zn—N) cm⁻¹. HRMS (APCI): m/z=1348.5456, (M⁺+1),oalocl. for C₉₂H₇₈N₅O₂Zn: 1348.5441 (error=+1.1 ppm).

FIG. 2 shows a synthesis scheme for preparing present dye P3 and P4.

A 100 mL round bottle flask was charged with dibronno porphyrin 4 (77mg, 0.1 mmol), ethynyl substituted perypene 6 (63 mg, 0.1 mmol),Pd(PPh₃)₄ (12 mg, 0.01 mmol), Et₃N (8 mL) and THF (40 mL) under argon.The reaction mixture was stirred at 50° C. for 24 hours. After removalof the solvents, the crude product was purified by column chromatography(silica gel, DCM:hexane=1:5) to give the purple solid product (59 mg),which was subjected into the next step of coupling reaction directly. Tothis purple solid was added 4-ethynylbenzoic acid (26 mg, 0.18 mmol),Pd(PPh₃)₄ (6 mg, 0.005 mmol), Et₃N (4 mL) and THF (20 mL) under argon.The reaction mixture was stirred at 50° C. for 24 hours. After removalof the solvents, the crude product was purified by column chromatography(silica gel, DCM:MeOH=50:1) to give the purple solid product P3 (50 mg,37% yield in two steps). Characterization for P3: ¹H NMR (500 MHz,CDCl₃) δ 9.91 (d, J=4.4 Hz, 2H), 9.69 (d, J=4.5 Hz, 2H), 9.15 (d, J=8.1Hz, 1H), 8.92 (d, J=7.6 Hz, 1H), 8.85 (d, J=7.5 Hz, 1H), 8.76-8.67 (m,4H), 8.24 (d, J=8.0 Hz, 2H), 8.19 (d, J=8.2 Hz, 1H), 8.16-8.09 (m, 3H),7.89 (s, 1H), 7.86-7.79 (m, 1H), 7.63 (q, J=8.4 Hz, 4H), 7.49(d, J=1.7Hz, 2H), 7.43 (s, 1H), 7.36 (s, 5H), 6.15 (s, 2H), 2.66(s, 6H), 1.93 (s,12H), 1.46 (s, 9H), 1.27 (s, 18H). ¹³C NMR (125 MHz, THF) δ 167.43,153.20, 152.92, 152.36, 151.05, 150.89, 150.81, 140.23, 140.18, 140.03,139.99, 138.61, 138.37, 136.39, 134.99, 133.04, 132.42, 132.21, 132.05,131.96, 131.76, 131.66, 131.26, 131.07, 130.96, 129.75, 129.25, 128.83,126.62, 126.28, 125.97, 125.83, 125.79, 125.59, 125.33, 123.20, 122.63,122.50, 121.98, 119.66, 119.46, 118.45, 117.98, 115.77, 103.21, 100.20,98.96, 98.47, 97.95, 97.00, 96.46, 51.08, 35.70, 34.37, 32.00,30.83,22.12, 21.79. IR (thin film) ν 3437.78 (OH), 2952.21 (CH₃), 2917.72(CH₂), 2849.90 (CH₃), 2176.56 (C≡C), 1638.48 (C═O), 1602.41 (C═C),1475.01 (C═N), 1296.05 (CH₂), 1264.32 (Ph), 1059.48 (Ph), 997.98 (Ph),853.25 (Ph, para), 795.93 (Ph, meta), 757.25 (Ph, meta), 713.89 (Ph,meta) cm⁻¹. HRMS (APCI): m/z=1374.5630, (M⁺+1) calcd. for C₉₄H₈₀N₅O₂Zn:1374.5598 (error=+2.3 ppm).

A 100 mL round bottle flask was charged with dibromo porphyrin 5 (142mg, 0.1 mmol), ethynyl substituted perypene 6 (63 mg, 0.1 mmol),Pd(PPh₃)₄ (12 mg, 0.01 mmol), Et₃N (8 mL) and THE (40 mL) under argon.The reaction mixture was stirred at 50° C. for 24 hours. After removalof the solvents, the crude product was purified by column chromatography(silica gel, DCM:hexane=1:8) to give the purple solid product (74 mg),which was subjected into the next step of coupling reaction directly. Tothis purple solid was added 4-ethynylbenzoic acid (22 mg, 0.15 mmol),Pd(PPh₃)₄ (5 mg, 0.004 mmol), Et₃N (4 mL) and THE (20 mL) under argon.The reaction mixture was stirred at 50° C. for 24 hours. After removalof the solvents, the crude product was purified by column chromatography(silica gel, DCM:MeOH=50:1) to give the purple solid product P4 (59 mg,29% yield in two steps). Characterization for P4: ¹H NMR (400 MHz,CDCl₃) δ 9.87 (d, J=4.4 Hz, 2H), 9.62 (d, J=4.4 Hz, 2H), 9.23 (d, J=8.1Hz, 1H), 8.92 (d, J=7.6 Hz, 1H), 8.85-8.79 (m, 4H), 8.73 (s, 1H), 8.17(ddd, J=24.9, 18.3, 8.0 Hz, 7H), 7.87 (s, 1H), 7.83 (d, J=8.0 Hz, 1H),7.73 (t, J=8.4 Hz, 2H), 7.64 (t, J=5.9 Hz, 4H), 7.52 (s, 2H), 7.45 (s,1H), 7.10 (d, J=8.5 Hz, 4H), 6.16 (s, 2H), 3.92 (t, J=6.4 Hz, 8H), 1.46(s, 9H), 1.30 (s, 18H), 1.05-0.68 (m, 92H). ¹³C NMR was not taken due toits low signal. IR (thin film) ν 3436.80 (OH), 2923.01 (CH₂), 2851.73(CH₃), 2186.01 (C≡C), 1689.64 (C═O), 1602.96 (C═C), 1455.93 (C═N),1296.02 (CH₂), 1247.74 (Ph), 1207.19 (CH₂), 1100.20 (Ph), 1061.63 (Ph),998.11 (Ph), 793.36 (Ph, para), 757.34 (Ph, meta), 723.11 ((CH₂)_(n),n>7), 711.28 (Ph, meta) cm⁻¹. HRMS (APCI): m/z=2027.1949, (M⁺+1) calcd.for C₁₃₆H₁₆₄N₅O₆Zn: 2027.1968 (error=−0.9 Ppm).

FIG. 3 shows device performance for various dyes P1, P2, and P3.

A 2.1-μm-thick, transparent layer of 22-nm-sized TiO₂ particles wasfirst screen-printed on FTO glass (Nippon Sheet Glass, Solar, 4 mmthick) and further coated with a 5.0-μm-thick second layer of scatteringtitania particles (WER4-O, Dyesol) to produce a bilayer titania film,which was used later as the negative electrode of a DSSC. Thepreparation procedures of TiO₂ nanocrystals and paste forscreen-printing were reported in a previous paper (Wang, P.;Zakeeruddin, S. M.; Comte, P.; Charvet, R.; Humphry-Baker, R.; Grätzel,M. J. Phys. Chem. B2003, 107, 14336). The film thickness was monitoredwith a bench-top Annbios XP-1 stylus profilometer. After sintering at500° C. and cooling to 80° C., a circular titania electrode (˜0.28 cm²)was stained by immersing it overnight into a solution of 150 μM dyedissolved in a binary solvent of tetrahydrofuran and ethanol (volumeratio, 1/4). The dye-coated titania electrode was then rinsed withacetonitrile and dried by air flow, and was further assembled with athermally platinized FTO positive electrode by a 25-μm-thick Surlyn(DuPont) hot-melt gasket and sealed up by heating. The internal spacewas perfused with an electrolyte with the aid of a vacuum-back-fillingsystem. Present cobalt electrolyte is composed of 0.25 Mtris(2,2′-bipyridine)cobalt(II) di[bis(trifluoromethanesulfonyl)imide],0.05 M tris(2,2′-bipyridine)cobalt(III)tris[bis(trifluoromethanesulfonypimide], 0.5 M TBP and 0.1 M LiTFSl inacetonitrile.

By “comprising” it is meant including, but not limited to, whateverfollows the word “comprising”. Thus, use of the term “comprising”indicates that the listed elements are required or mandatory, but thatother elements are optional and may or may not be present.

By “consisting of” is meant including, and limited to, whatever followsthe phrase “consisting of”. Thus, the phrase “consisting of” indicatesthat the listed elements are required or mandatory, and that no otherelements may be present.

The inventions illustratively described herein may suitably be practicedin the absence of any element or elements, limitation or limitations,not specifically disclosed herein. Thus, for example, the terms“comprising”, “including”, “containing”, etc. shall be read expansivelyand without limitation. Additionally, the terms and expressions employedherein have been used as terms of description and not of limitation, andthere is no intention in the use of such terms and expressions ofexcluding any equivalents of the features shown and described orportions thereof, but it is recognized that various modifications arepossible within the scope of the invention claimed. Thus, it should beunderstood that although the present invention has been specificallydisclosed by preferred embodiments and optional features, modificationand variation of the inventions embodied therein herein disclosed may beresorted to by those skilled in the art, and that such modifications andvariations are considered to be within the scope of this invention.

By “about” in relation to a given numerical value, such as fortemperature and period of time, it is meant to include numerical valueswithin 10% of the specified value.

The invention has been described broadly and generically herein. Each ofthe narrower species and sub-generic groupings falling within thegeneric disclosure also form part of the invention. This includes thegeneric description of the invention with a proviso or negativelimitation removing any subject matter from the genus, regardless ofwhether or not the excised material is specifically recited herein.

Other embodiments are within the following claims and non-limitingexamples. In addition, where features or aspects of the invention aredescribed in terms of Markush groups, those skilled in the art willrecognize that the invention is also thereby described in terms of anyindividual member or subgroup of members of the Markush group.

1. A dye-sensitized solar cell comprising a dye molecule of Formula (I):

wherein: M is zinc, cobalt, nickel, iron, or copper; each of L₁ and L₂is a linker and is independently selected from the group consisting of adirect bond and an ethynylene group; each of R₁, R₂, R₃, R₄, R₅, R₆, R₇,R₈ is independently selected from the group consisting of hydrogen,halogen, C₁₋₃₀ alkyl, and C₆-C₂₀ aryl; each of R₉ and R₁₀ isindependently a substituted or unsubstituted phenyl, or a substituted orunsubstituted benzyl; AG is an anchor group for attachment to asubstrate; and Pery is a perylene-based moiety of Formula (II):

wherein: each of R₁₁ and R₁₂ is independently a substituted orunsubstituted phenyl, or a substituted or unsubstituted benzyl.
 2. Thedye-sensitized solar cell of claim 1, wherein R₁₁ is a substituted orunsubstituted benzyl and R₁₂ is a substituted or unsubstituted phenyl.3. The dye-sensitized solar cell of claim 2, wherein R₁₂ is a mono-,di-, tri-, tetra-, or penta-substituted phenyl.
 4. The dye-sensitizedsolar cell of claim 2, wherein R₁₂ is a C₁₋₁₀ alkyl-substituted phenyl.5. The dye-sensitized solar cell of claim 4, wherein R₁₂ istert-butylphenyl.
 6. The dye-sensitized solar cell of claim 5, whereinR₁₂ is para-tert-butylphenyl.
 7. The dye-sensitized solar cell of claim2, wherein R₁₁ is a mono-, di-, tri-, tetra-, or penta-substitutedbenzyl.
 8. The dye-sensitized solar cell of claim 7, wherein R₁₁ is aC₁₋₁₀ alkyl-substituted benzyl.
 9. The dye-sensitized solar cell ofclaim 8, wherein R₁₁ is a di-C₁₋₁₀ alkyl-substituted benzyl.
 10. Thedye-sensitized solar cell of claim 9, wherein R₁₁ is3,5-di-tert-butylbenzyl.
 11. The dye-sensitized solar cell of claim 1,wherein R₉, or R₁₀, or both R₉ and R₁₀ are substituted or unsubstitutedphenyl.
 12. The dye-sensitized solar cell of claim 11, wherein each ofR₉ and R₁₀ is independently a mono-, di-, tri-, tetra-, orpenta-substituted phenyl.
 13. The dye-sensitized solar cell of claim 12,wherein R₉, or R₁₀, or both R₉ and R₁₀ are independently C₁₋₁₀alkyl-substituted phenyl.
 14. The dye-sensitized solar cell of claim 13,wherein R₉, or R₁₀, or both R₉ and R₁₀ are methylphenyl.
 15. Thedye-sensitized solar cell of claim 14, wherein R₉, or R₁₀, or both R₉and R₁₀ are trimethylphenyl.
 16. The dye-sensitized solar cell of claim15, wherein R₉, or R₁₀, or both R₉ and R₁₀ are 2,4,6-trimethylphenyl.17. The dye-sensitized solar cell of claim 12, wherein R₉, or R₁₀, orboth R₉ and R₁₀ are independently a C₁₋₁₅ alkoxy-substituted phenyl. 18.The dye-sensitized solar cell of claim 17, wherein R₉, or R₁₀, or bothR₉ and R₁₀ are octyloxyphenyl.
 19. The dye-sensitized solar cell ofclaim 18, wherein R₉, or R₁₀, or both R₉ and R₁₀ are2,6-di-octyloxyphenyl.
 20. The dye-sensitized solar cell of claim 17,wherein R₉, or R₁₀, or both R₉ and R₁₀ are dodecyloxyphenyl.
 21. Thedye-sensitized solar cell of claim 20, wherein R₉, or R₁₀, or both R₉and R₁₀ are 2,6-di-dodecyloxyphenyl.
 22. The dye-sensitized solar cellof claim 1, wherein AG comprises a phenolic derivative of benzoic acid.23. A dye molecule of Formula (I):

wherein: M is zinc, cobalt, nickel, iron, or copper; each of L₁ and L₂is a linker and is independently selected from the group consisting of adirect bond and an ethynylene group; each of R₁, R₂, R₃, R₄, R₅, R₆, R₇,R₈ is independently selected from the group consisting of hydrogen,halogen, C₁₋₃₀ alkyl, and C₆-C₂₀ aryl; each of R₉ and R₁₀ isindependently a substituted or unsubstituted phenyl, or a substituted orun sub stituted benzyl; AG is an anchor group for attachment to asubstrate; and Pery is a perylene-based moiety of Formula (II):

wherein: each of R₁₁ and R₁₂ is independently a substituted orunsubstituted phenyl, or a substituted or unsubstituted benzyl.